kidney structure and function Flashcards
name the urinary system components
2 kidneys (left and right) & 2 ureters (left and right),
urinary bladder & urethra
define Nephrology
scientific study of anatomy, physiology & pathology of kidney
define urology
branch of medicine dealing with male & female urinary systems & male reproductive system.
what are the kidney functions
regulation of blood iron composition
maintenance of blood osmolarity
regulation of blood volume
Regulation of blood pressure
regulation of blood PH
release of hormones
regulation of blood glucose levels
secretion of waste and foreign substances
explain kidneys regulation of blood iron composition
Na+, K+, Ca2+, Cl-, [HPO4]2-
explain kidneys maintenance of blood osmolarity
by separately regulating loss of water & solutes in urine, maintains 290mOsm/litre
explain kidneys regulation of blood volume
by conserving or eliminating water
explain kidneys regulation of blood pressure
Adjusting blood volume:
- Reduced blood volume = reduced blood pressure
Renin secretion:
- activates renin-angiotensin pathway
——–> Increase vasoconstriction & blood volume = increased blood pressure
Adjusts renal resistance:
- encountered by blood flowing through kidneys which in turn affects systemic vascular resistance
——-> Increased renal resistance = increased blood pressure.
explain the Renin-Angiotensin Pathway
for angiotensin II formation
liver produces angiotensinogen, which goes into blood stream with renin from kidney to produce angiotensin I. it then gets angiotensin converting enzyme from lung capillaries to form angiotensin II. which goes on to:
- vasoconstriction
- increased aldosterone secretion
- increased ADH secretion
- increased thirst
explain kidneys in regulation of blood pressure
excrete variable amount H+ into urine & conserve bicarbonate which buffers H+
explain kidneys in release of hormones
calcitriol
- regulate calcium homeostasis by increase absorption from foods in GI
erythropoietin
- stimulates RBC production
explain kidneys in regulation of blood glucose level
deaminate glutamine, use it for synthesising new glucose
explain kidneys in secretion of waste and foreign substances
in urine, due to body metabolism:
ammonia & urea
- from deamination of amino acids
bilirubin
- from catabolism of Hb
creatinine
- from breakdown of creatinine phosphate in muscles
uric acid
- from catabolism of nucleic acids
drugs & environmental toxins
wheres the kidneys found in body
paired just above the waist
At concave side:
all blood & lymphatic vessels, nerves & ureter enter/leave by the renal hilum
what 3 layers pf tissue are the kidneys surrounded by
renal capsule - transparent
adipose capsule - fat pad
renal fascia - connective tissue, attaches to posterior abdominal wall
name 2 distinct regions of kidneys internal anatomy
renal cortex
renal medulla
explain kidneys renal cortex
outer, smooth, reddish
the portions that extend between renal pyramids = renal columns
explain kidneys renal medulla
inner, reddish-brown
consists of 8-18 cone-shaped renal pyramids; apex (renal papilla) points to centre
what is the kidneys renal parenchyma
functional portion of kidney
composed of renal cortex + renal pyramids
explain kidneys nephrons
Functional unit of the kidney
within parenchyma, ~1 million microscopic units.
explain the travel of urine
urine is formed in nephron
then goes to:
papillary ducts = collecting ducts (several hundred)
then to:
minor (n=8-18) —-> major (2-3) calyces (cups)
(1 minor receives from ducts of 1 papilla)
then to:
renal pelvis (large single cavity)
then to:
ureter
then to:
urinary bladder
name the 2 parts to the nephron
renal corpuscle
renal tubule
explain the nephrons renal corpuscle
(filters plasma)
Glomerulus:
- mass of capillary loops
Bowman’s Capsule:
- glomerular capsule surrounds glomerulus
explain the nephrons renal tubule
(into which filtered fluid passes)
- proximal convoluted:
attached to Bowman’s capsule - Loop of Henle:
descending, hairpin, ascending - distal convoluted tubule
name the 2 positions of nephrons and what % of nephrons are in these types
cortical: 80-85%
juxtamedullary: 15-20%
the renal corpuscles lie where in cortical and juxtamedullary positions of nephrons
cortical:
Outer portion of renal cortex
JUXTAMEDULLARY:
Deep in cortex, close to medulla
explain loops of henle in the cortical and juxtamedullary positions of nephron
cortical:
Short, mainly in cortex, slightly penetrate medulla
juxtamedullary:
Long, extend deep into medulla
explain the different blood supply to loops in the cortical and juxtamedullary positions of nephrons
cortical:
From peritubular capillaries arising from efferent arterioles
juxtamedullary:
From peritubular capillaries & vasa recta arising from efferent arterioles
explain the different ascending loop limbs in cortical and juxtamedullary positions of nephrons
cortical:
Thick only
juxtamedullary:
thin, then thick
what do the thick & thin segments of ascending limb loop actually refer to
height of epithelium and not the diameter of the lumen.
do kidneys have blood vessels and why
Abundantly supplied with blood vessels
removes waste from blood & regulates its volume & composition
describe kidneys resting cardiac output
Although kidneys <0.5% body mass, receive 20-25% resting cardiac output via L + R renal arteries
what is adult renal blood flow in L/min
1.2 L/min.
summarise the path of blood flow through the kidney
from renal artery to arterioles
to glomerular capillaries
to efferent arterioles
to peritubular capillaries
to veins
i.e., large to small arteries to small to large veins.
describe the looping pattern of vasa recta
it loops around the efferent arterioles, one side is ascending vasa recta (blue coloured) and one side is descending vasa recta (red coloured)
what are the 2 components of the renal corpuscle
Bowman’s capsule
glomerulus
explain the SEM of renal blood vessels
Several glomeruli & other blood vessels in kidney
High Power SEM of a single glomerulus (in a renal corpuscle)
what cells forms the entire wall of the glomerular capsule, renal tubule & ducts
a single layer of epithelial cells
Although epithelial cells forms the entire wall of the glomerular capsule, renal tubule & ducts, each part has what?
distinctive histological features that reflects its particular function
explain the Glomerular Capsule outer and inner layers
Outer parietal layer wall of simple squamous epithelium
Inner visceral layer of specialised simple squamous epithelial cells = podocytes
what do podocytes do
wrap around the glomerular capillaries
pedicles allow what
filtration
explain Podocytes structure and function
have foot-like projections (pedicels) to cover capillaries
Allow filtration slits (gaps) to be formed
capillaries are……
fenestrated
what make up the filtration membrane
Podocytes and fenestrated capillaries
the membrane is 0.1mm thick
explain the filtration membrane
Fluid filtered from the capillaries (passed through basement membrane) passes filtration slits to enter the capsular (Bowman’s) space [between the 2 layers of the capsule]
what passes from blood to capsular space?
To space (if molecule <6nm diameter):
H2O
Glucose
Vitamins
Amino acids
Very small plasma proteins
Urea
Ammonia
Ions
what doesn’t pass from blood to capsular space and so stays in blood
Albumen (7.1nm)
Plasma proteins
Platelets
RBC & WB
describe the Renal Tubule & Collecting Duct histology
Prominent brush border of microvilli in proximal convoluted tubule cells, to
increase surface area for reabsorption & secretion
in a microscopic image:
- the proximal convoluted tubule, does not have a clear centre due to presence of microvilli. Whereas distal convoluted tubule has no microvilli and so can see a clear, white centre of the tubule.
- Black dots: = renal corpuscle
- Blue & white dots = distal convoluted tubule
- Red & yellow dots = proximal convoluted tubule.
explain the Juxtaglomerular Apparatus (JGA)
In each nephron, final portion of ascending limb (columnar & crowded = macula densa) makes intimate contact with afferent arteriole (modified SMC = juxtaglomerular cells) serving that renal corpuscle
Together called JGA
Secretes renin (JG cells) (regulates BP within kidneys)
the Last portion of distal collecting duct has what 2 cells types
principal cells
intercalated cells
explain the Last portion of distal collecting ducts principal cells
most of the cells are these
theyre Receptors for ADH & aldosterone
explain the Last portion of distal collecting ducts intercalated cells
fewer of the cells are these
theyre Apical microvilli & many mitochondria
Play role in haemostasis of blood pH
Drain to large papillary ducts
are lines by what cells
simple columnar epithelial cells.
